feat(frontend): add API client, layout, and routing

- Create Axios-based API client with sources, jobs, and dashboard endpoints
- Add responsive Layout component with navigation sidebar
- Set up React Router with Dashboard, Backups, and Settings routes
- Configure TanStack Query provider with default options
- Use lucide-react for navigation icons

frontend/node_modules/dom-helpers/cjs/isInput.js

@@ -0,0 +1,16 @@
+"use strict";
+
+exports.__esModule = true;
+exports.default = isInput;
+var regExpInputs = /^(?:input|select|textarea|button)$/i;
+/**
+ * Checks if a given element is an input (input, select, textarea or button).
+ * 
+ * @param node the element to check
+ */
+
+function isInput(node) {
+  return node ? regExpInputs.test(node.nodeName) : false;
+}
+
+module.exports = exports["default"];